I have an opportunity to buy an older essence, but the neck seems to be pulling to the treble side. The treble truss rod is as loose as can be, and the bass one is quite a bit tighter with a lot more thread showing (~3/8 inch)

I can't get the relief on the bass side less then around .013" without the treble side pulling completely flat. Also, somewhere around the 12th fret, when sighting down the neck, you can clearly see the neck turn towards the treble side on both edges of the fret board.

What could've caused this? Any remedies or is this pretty much a case of set it up as best as possible and ignore it?

I don't know what the best course of action is. I think I might take the strings off, loosen both nuts completely, and let it sit for a week or so in a room that's not too dry or too humid, just to see where the neck wants to go with no tension on it. But I'm not a luthier, and I don't know. Hopefully, some other folks will chime in with more knowlegable suggestions.

Other than that the pieces of wood happened to have a natural inclination to bend in that direction, the only other thought is that it wore mis-matched strings for many years with more tension on one side to train the neck to bend in that direction. As far as repairing such a thing goes, you'd best talk to Mica for advice. If it can't be resolved with clamps and/or heat, you're probably looking at more than the bass is worth to replace the neck.

Without actually seeing it, I would concur with the previous posters - I think you're looking at a bass with a bad neck. Each instrument and each piece of wood is different and subject to doing something unpredictable in the future.

The kinds of behavior you're describing isn't the result of a misadjusted or broken truss rods. The opposing tension of the laminates helps hold things straight and true, but it doesn't look like it worked in this case.

If that's the case, your best case scenario is a refret and levelling, but the worst case can be pretty bad - neck replacement which certainly won't be worth it.

For what it's worth, the back of the neck on this thing is unfinished-- no idea if that was from the factory or someone took sandpaper to it (though it is factory smooth feeling)... It looked like it hadn't been oiled in 10 years; I can't imagine that did much to keep things straight!

It's twisted, but not HORRIBLY so; I wonder what it would cost to have it straightened? Do you think this is something someone could do locally or should I send it back to it's birthplace?

If the neck is really unfinished, that would have been done after it was purchased, probably sanded down by someone who wanted to make it smoother and therefore faster. The finish protects the wood; so that when you remove the finish, you are removing the protection. This may have contributed to the twisting. If cost were no object, sending it back to the shop would be the best way to go. If there is no finish on the neck, a refinish at the shop is not inexpensive. A refinish and the neck work would probably cost more than a similar Essence in good condition would sell for on the used market. You may want to take it to a good local luthier and have them give an opinion on what they would do and what it would cost. It may be the case that, as David suggested, a refret and levelling may make this bass work at a fairly reasonable cost.

Honestly, the neck warp isn't a huge deal, I wish that was the only problem. It's tilted in such a way that the treble side gets flatter relief, which is kind of ideal anyhow. The bigger problem is the actual pull to the treble side-- the strings aren't centered and it looks pretty off and plays a bit close to the edge on the G. I straightedged both sides of the neck and it's off by a considerable and very saddening margin. Ain't no amount of fret leveling fixing that. :-( It's too bad; it is a pretty boat oar though.

The neck sure looks like it was never finished and doesn't appear to be a sand job, but I've never heard of or seen an Alembic that came out of the factory like that... we'll see what comes out of the SN lookup. I somehow believe that the folks in Santa Rosa wouldn't let a maple neck out the door with no finish no matter what the customer wanted...

Are you sure the neck is really unfinished and not just a satin finish? Satin finished necks can often feel unfinished. If this is an unfinished maple neck, then it should show significant dirt, oil, and discoloration - the type you often see on an old Fender Tele or Strat with a maple fingerboard. If it's maple and clean looking, it's most likely a satin finish.

Im by no means an expert (the guys here can vouch for that!) but the simple fact that one truss rod is real tight and the other is loose would send alarm bells ringing to me!

This is undoubtedly allowing for (or causing) twist in the neck in my opinion! I would back them both off, as Dave suggested, take the nuts off - let the neck settle for a couple of days - and start over!

In my mind a neck with two rods shouldnt have a large amount of difference like this.